Okay, did one more test for you to rule out XAMPP/WAMP.
I downloaded the latest Apache 2.4.10 Win32 build from apachelounge.com.
I then downloaded the latest PHP 5.6.0 build from windows.php.net.
I then configured PHP manually in httpd.conf for Apache 2.4.
I turned on the GD extension for PHP.
I then redownloaded a fresh copy of the .zip download from getgrav.org and extracted it to /htdocs.
I then encountered the exact same problem. I then once again set css_pipeline to false in user/config/system.yaml, and it once again works.